Latch mechanism



Dec. 25, 1962 J. A. MORRISON E'rAL LATCH MECHANISM 2 Sheets-Sheet l Filed Sept. l5, 1960 l .IIIJII-I Dec. 25, 1962 J. A. MORRISON ETAL 3,(1)7,3`95

LATCH MECHANISM Filed Sept. 15, 1960 2 Sheets-Sheet 2 W L6-MMM priv:

3,970,395 LATCH MECHANISM `lohn A. Morrison, Eugene Schickler, and Theodore W. Schmidt, Seattle, Wash., assignors to Boeing Airplane Company, Seattle, Wash., a corporation of Delaware Filed Sept. 13, 1960, Ser. No. 55,634 4 Claims. (Cl. 292-113) The present invention is of the general nature of that disclosed in the Patent No. 2,752,186 to Morrison, one of the joint inventors herein, dated .Tune 26, 1956. The invention concerns a wholly submerged latch mechanism useful in retaining adjoining cowl panels of an aircraft in closed position, but enabling ready disengagement of the latch by a tool such as a screwdriver applied to a handle element of the latch mechanism, through a hole provided in one of the panels. This, of course, is a specific use, illustrative of other uses to -which the invention may be put.

The latch mechanism of the prior patent required, for release, the insertion of a screwdriver point or similar tool, to depress and disengage a safety catch which was separate from the latch proper, the tool in so doing becoming wedged in the actuating member of the latch mechanism whereby the actuating member could be swung laterally on a pivot to eifect withdrawal of a bolt or pin from engagement with the opposite panel. Entire reliance was placed on the safety catch to retain the actuating member and the bolt in locking position, and in turn reliance was placed on a spring to retain the safety catch in its secured position. The latch was in no sense selfdisengaging, but required extended positive unlatching movement by the inserted tool, and often a prying action which damaged one or both panels. According to the present invention a connection is made from the one panel, on which is mounted the latch mechanism to the opposite panel through a device which produces a force past center alignment of two of the points of securement involved, and which therefore cannot become unlatched without returning parts past the dead center position, but upon such return is virtually self-releasing. Moreover, parts are held in the secured position by a latch member which is positively retained in secured position, to retain the other elements in their past center position, which latch element is directly engageable with a tool to swing it to its unsecured position, and to initiate movement of the several elements of the mechanism to the opposite side of the dead center position, so that once past that position the release of the latch is simple and virtually automatic.

As a result of the novel mechanism in this invention, wear on the releasing portions of the mechanism and upon the surrounding portion of the panel which supports them is slight. No deforming forces are needed to eifect disengagement. The entire latch mechanism is disposed interiorly of one panel, and an end may come iush with the surface of the panel, thereby to afford the minimum of interruption to the smoothness of the surface defined by the panels skin, and so to lessen the drag produced in high speed flight by such cowl latches.

There is also provided by this invention a simple, easily manufactured, and light-weight cowl latch mechanism which produces the minimum of weight penalty when used in aircraft constructions. Moreover, the cowl latch mechanism of this invention may be designed to assume appreciably greater loads than previously known elements for similar purposes, including that of the Morrison patent, and thereby contributes to lightness in that a smaller number of cowl latch mechanisms are required to accomplish the Same eective securement as the earlier designs required a large number of latch mechanisms.

These and other objects will be more readily ascernited States Fate tained from a study of the accompanying drawings, of this specification, and of the claims which terminate the same.

FIGURE 1 is an isometric view of the cowl latch mechanism in secured position, showing it in relation to the interior construction of the two cowl panels, which panels are in part broken away.

FIGURE 2 is an interior plan view of the latch mechanism in the secured position of parts.

FIGURE 3 is an enlarged underside plan view of the latch mechanism from the exterior of a cowl panel.

FIGURE 4 is a side elevational View partly broken away, illustrating the latch mechanism in secured position. FIGURE 5 is a similar view showing the latch mechanism at the instant of disengagement, and FIG- URE 6 is a similar view showing the disengagement completed and the panels about-to separate.

Representative panels A and B are disclosed, which when secured together abut along a common edge. Usually one or both these panels would be hingedly mounted along the opposite edge to swing outwardly, somewhat as indicated by the arrow in FIGURE 6. One of these panels supports an eye E which extends across the meeting line of the two panels, and which normally would be iixed to the panel B.

Somewhat inwardly from the common edge of the two panels the skin of the panel A is provided with a hole H. This is the only hole through this panel for any given latch mechanism, and the secured latch and its release mechanism is accessible only through the hole, which is of minimum size. Interiorly of the p-anel skin is located a link 1, having a hooked end 1t) which will engage the eye E. The link is of general dog-leg shape, the longer arm carrying the hook 10 at its end and the shorter arm being arranged for pivotal mounting of the link as a whole at 11 upon a handle element 2. This handle element is pivotally mounted at 2t) upon the panel A in the vicinity of the hole H. The handle element is in fact a lever, one end of which, designated 2,1, is of general arcuate shape concentric with the pivot mount at 20, and the opposite end of which, designated 22, extends from the pivot 20 oppositely to the end 21, so that the handle lever in effect is pivotally mounted between its ends. It is the end 22 which is pivoted at 11 to the shorter end of the hooked link 1.

The arcuate end 21 of the handle lever 2 in the secured position of the parts lies within the hole H, substantially flush with the skin of the panel A. Preferably, although not necessarily, the handle lever 2 is of hollow construction, whereby the outer ,end is recessed, and a latch member is supported within this recess. This latch member is designated in general by the numeral 3. It is preferably of a construction embodying three separate elements, however. The element 3 is hollow or of U-shape in cross section and is pivotally mounted at 30 adjacent the outer end of the arcuate portion 21 of the handle elever 2. Also pivotally mounted here at 30 is a block 31 which will undergo rocking movement relative to the member 3 between two limit positions in one of which it abuts the wall or the recess adjacent the pivot 20. The block 31 has a recess 32 of a shape to receive the tip of a screwdriver S to manipulate the latch. The third element comprises a'securing member 33 which is pivoted at 34 upon the member 3 in abutting relation to the block 31. The pivot at 34 includes a pin which extends completely through the element 3 and protrudes at one or both its ends, and which protrudes also through an oversize hole or holes 23 in the arcuate end 2.1 into a position where it can engage the link 1. The link 1 is preferably of double construction so that it straddles the handle lever 2 (see FIGURES l and 2), and the link is recessed at 13, the recess as shown being of hook-like form, whereby the protruding ends of the pin 34 may engage in this recess and latch the link 1 in its secured position. A light spring 35 urges the element 33 and thereby the entire latch device 3 towards secured position about the pivot at 30. Also and preferably a spring 12 reacting between the short leg of the link 1 and the correspondingy end 22 of the handle member 2, urges the link 1 to disengage its hook from the eye E. The counter directional action of the spring 12 through the handle member and the pin 34 prevents this, however, until the pin has been disengaged from the recess 13, which step will be explained.

It will be observed (see FIGURE S) that when parts are in the latched position the pivot at 11 is outwardly of a line C, which extends through the eye E or the hook 10 and the pivotal mount at 20. The dog-leg form of the link 1 permits this construction. So arranged, tension in the link 1 effective along a line below the line C tends to retain all parts of the latch mechanism in secured position. When disengagement is required it is only necessary to insert a screwdriver S within the recess 32, which is freely accessible, and to rock the block 31 slightly about its pivot at 30. This tends also to rock Athe entire latch assembly, including the member 3, in the same sense about the pivot 30, and when parts reach the position of FIGURE 5 the pin 34 has been withdrawn from the recess 13 in the link 1. Parts are, however, still in the over-center position and it requires some slight counter-clockwise rotation of the handle lever 2 about its pivotal mount at 20 to shift the pivot mount at 11 past the line C and so to apply the tensional forces above this line to release of the link 1 from the eye E. This occurs easily and immediately following movement of the pivot at 11 past the line C, and parts immediately reach the position shown in FIGURE 6 without the necessity of applying forces to disengage the latch mechanism other than those which are employed in rocking the elements 31 and 3.

When the latch mechanism is to be reengaged it is only necessary to rotate the handle lever 2 clockwise from the position of FGURE 6. The links hooked end 16 is held by a stop 4, and is prevented from going too far in the opposite direction by a spaced stop 4) in position to engage the eye E. Now when the handle lever 2 is rotated in the clockwise sense, parts will return to the position of FIGURE 4, and the pivotal rocking of the element 3 about the pivot at 30 will enable the pin 34 to ride over the cammed surface of the link which leads to the recess 13, and so to snap the pin 34 into the recess under F the inuence of the spring 35. All parts return to their secured position and the skin of the panel A is substantially uninterrupted.

A further advantage of the cowl latch mechanism of this invention is that there can be no question whether a given latch mechanism is secured or not. lf it is secured, all parts are submerged within the panel that supports it. If it is not secured there is protrusion of the handle lever 2, or at least of its arcuate end 21, through the hole H, or part No. 3 will remain substantially in the position shown in FIGURE 5.

We claim as our invention:

l. A latch mechanism engageable with a keeper member and including a lever Inember mounted for pivotal movement about a fixed axis extending between its ends, a link member having hook means on one end portion thereof for engagement with the keeper element and the other end portion thereof connected to one end portion of the lever member for relative pivotal movement about a second axis parallel to the fixed axis and, in the keeper engaged position of the link member, extending to one side of a plane of the fixed axis intersecting the hook means, resilient means urging the lever and link members to pivot about the second axis in opposite angular directions, the other end portion of the lever member being arcuately formed about the fixed axis and defining an end recess therein which opens laterally of the lever member through an aperture therein, a latch mounted in the end recess for rocking movement between two limit positions, in one of which the latch abuts the wall of the recess adjacent the xed axis, said latch having a pin thereon extending through said aperture and laterally outwardly of the lever member, sai-d link member having a recess therein disposed to engage the pin in one limit position of the latch, corresponding to said keeperengaged position of the link member, and to disengage the pin in the wall abutting position of the latch, and means on said latch for engagement by a tool whereby rocking movement of the latch into said wall-abutting position actuates said lever mem-ber to pivot the second axis to the opposite side of said plane and effect disengagement` of the link member from the keeper element.

2. A latch mechanism according to claim l wherein `the latch comprises a U shaped member mounted in the lever end recess for limited rocking movement about a third axis extending parallel to the fixed axis adjacent the end opening of said lever end recess, a first block mounted in the U shaped member for rocking movernent relative thereto about said third axis and between said limits, and a second block mounted in abutting relation to the rst block in the U shaped member for limited rocking movement relative to the U shaped member about a fourth axis parallel to the third axis, said pin extending along said fourth axis and said means for tool engagement including a recess in the first block adapted to receive a screw driver or the like.

3. A latch mechanism according to claim 2 further comprising resilient means mounted in the lever end recess to urge the pin into engagement with the recess in the link member.

4. A latch mechanism according to claim 3 wherein the recess in said link member opens radially outwardly from the second axis to receive the pin when the latch is rocked in a clockwise angular direction relative to the second axis.

References Cited in the le of this patent UNITED STATES PATENTS 2,712,955 Andrews Iuly l2, 1955 2,752,186 Morrison June 26, 1956 2,904,141 Henrichs Sept. l5, 1959 

